lib/genalloc.c: use vzalloc_node() to allocate the bitmap

Some devices may have big memory on chip, such as over 1G.  In some
cases, the nbytes maybe bigger then 4M which is the bounday of the
memory buddy system (4K default).

So use vzalloc_node() to allocate the bitmap.  Also use vfree to free
it.

Link: http://lkml.kernel.org/r/20181225015701.6289-1-sjhuang@iluvatar.ai
Signed-off-by: Huang Shijie <sjhuang@iluvatar.ai>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Alexey Skidanov <alexey.skidanov@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

lib/genalloc.c

@@ -187,7 +187,7 @@ int gen_pool_add_virt(struct gen_pool *pool, unsigned long virt, phys_addr_t phy
 	int nbytes = sizeof(struct gen_pool_chunk) +
 				BITS_TO_LONGS(nbits) * sizeof(long);
 
-	chunk = kzalloc_node(nbytes, GFP_KERNEL, nid);
+	chunk = vzalloc_node(nbytes, nid);
 	if (unlikely(chunk == NULL))
 		return -ENOMEM;
 
@@ -251,7 +251,7 @@ void gen_pool_destroy(struct gen_pool *pool)
 		bit = find_next_bit(chunk->bits, end_bit, 0);
 		BUG_ON(bit < end_bit);
 
-		kfree(chunk);
+		vfree(chunk);
 	}
 	kfree_const(pool->name);
 	kfree(pool);